Polymerase chain reaction (PCR) is a molecular biology technology used for expanding specific deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) segments. Typical polymerase chain reaction apparatus repeats a thermal cycling procedure to perform a repetitive process of heating and cooling using a thermocycler. Thermal energy is gradually transferred to a reaction tube through a metal block to tuning the reacting temperature, such that the DNA or RNA segments can react undergo at three different temperature conditions, namely, denaturation (95° C.), adhesion (45° C.-65° C.) and extension (72° C.). Conventionally, the thermal cycling procedure is performed through multi-level indirect heating, which not only consumes a large amount of time but also requires a large machine volume, the detection efficiency of the traditional PCR and the application scope thereof may thus be rather limited.
A convective polymerase chain reaction (cPCR), is a special type of PCR based on the principle of thermal convection, the reaction vessel containing a reaction solution is directly heated, such that the reaction solution generates temperature gradient and causes thermal convection. The reaction solution can move around the reaction vessel, and the temperature of the reaction solution can keep changing along the convection path of the reaction solution, whereby the expansion of the nucleic acid can be completed along with the convection path of the reaction solution instead of changing the temperature of the whole reaction solution. The nucleic acid expansion time thus can be shorten, the apparatus and instrument for performing the polymerase chain reaction can be simplified and the detection cost may be reduced. Currently the convective polymerase chain reaction apparatus includes a reaction vessel formed of plastic tube or glass capillary, a light source disposed under the bottom of the tube and providing a light beam to excite the fluorescent reagent inside the tube to generate a fluorescence signal, and a detector used to detect the fluorescence signal to achieve the object of monitoring the polymerase chain reaction.
However, since the reaction solution of polymerase chain reaction typically includes a biological specimen (such as the whole blood of an organism) that may has a very complicated ingredients, thus most residues of the reaction solution (such as protein, blood cells) may decapitate at the bottom of the capillary to interfered and obstructed the optical path of the incident light beam and the excited fluorescence signal. Consequently, the light beam cannot pass through the bottom of the tube to excite the fluorescent reagent inside the tube, the fluorescence signal cannot be received by the detector on the tube-wall, and the performance and the process control of the polymerase chain reaction is severely affected.
Therefore, there is a need to provide an advanced convective polymerase chain reaction apparatus and an optical detecting method thereof to obviate the drawbacks and problems encountered from the prior art.